Field of the Invention
The present invention relates to an image sensor unit, an image reading apparatus, and an image forming apparatus.
Description of the Related Art
Some of image reading apparatuses such as scanners and image forming apparatuses such as copying machines or multifunction printers (MFPs) incorporate a contact image sensor. In such image reading apparatuses and image forming apparatuses, the contact image sensor reads an object to be read while relatively moving with respect to the object to be read. In this process, the distance between the contact image sensor and the object to be read is kept at a distance suitable for reading by a distance adjusting member provided in the contact image sensor. In general, the contact image sensor has a shallow depth of focus. Thus, the quality (such as resolution) of reading of an image by the contact image sensor is affected by the dimensional tolerance of each component of the contact image sensor. Thus, the resolution of reading varies (differs) between individual contact image sensors due to the dimensional tolerance of each component of the contact image sensor.
A possible configuration for adjusting the distance to the object to be read for each contact image sensor is a configuration in which a sheet-like member (distance adjusting member) of a predetermined thickness is interposed between a housing of the contact image sensor and a spacer (distance keeping member). With such a configuration, however, a plurality of types of sheet-like members of different thicknesses need to be prepared in advance. Thus, the types of the members involved in the adjustment of the distance to the object to be read increase.
As another configuration for adjusting the distance to the object to be read, Patent Document 1 discloses a configuration that involves a cam mechanism. With the configuration, the distance to the object to be read can be adjusted for each contact image sensor by rotation of a cam. With the configuration, however, the contact image sensor needs to have a region where the cam mechanism is provided, and the housing has an increased size. In addition, the number of components increases, and the structure is complicated, so that the manufacturing cost increases.
Patent Document 1: Japanese Laid-open Patent Publication No. 2009-164743